Conventionally, automatic teller machines (ATMs) and money exchangers have been equipped with apparatuses for authenticating bills.
Moreover, apparatuses for authenticating bills have also been provided for automatic vending machines, gaming machines such as slot machines and pachinko gaming machines that dispense game media such as medals, coins, and gaming balls used in games according to the contents of prizes of the games, money exchangers or prepaid card vending machines equipped in game arcades where those gaming machines are installed, and further, so-called ball dispensers (so-called sandwiched devices) arranged between pachinko gaming machines.
These types of authentication apparatuses include ones that compares received light data acquired from a bill to be authenticated and received light data of a genuine bill prepared in advance to make a determination, using received light data of a transmitted light and a reflected light acquired by irradiating light onto bills.
For example, there has been a technique for authentication by alternately irradiating red light and infrared light onto a bill to provide a transmitted light per one scanning of each of the red light and infrared light as image data, sectioning this image data into a plurality of sections, and authenticating the bill based on a difference between the maximum value and minimum value per each section (see Patent Document 1, for example).
Moreover, a technique for irradiating visible light rays and infrared rays onto a bill to generate, for each reflected light thereof, two types of received light data according to the brightness/darkness of the reflected light and using a difference between these two types of received light data for a determination has also been known (see Patent Document 2, for example).    Patent Document 1: Japanese Published Unexamined Patent Application No. H10-312480    Patent Document 2: Japanese Published Unexamined Patent Application No. 2005-234702